Solstice Sunset

Last night was the "sunset expedition" - the first time this season that the sun set behind Kitt Peak National Observatory (KPNO). After an announcement on the Tucson Amateur Astronomy Association's forum, there was a little interest in observing it, so the sunset hunt was on! In all we had 8 people and 7 scopes or lenses focused on the sunset.

We met at the McDonald's on Tanque Verde and Catalina Highway at 4pm. Melinda and I were the last to arrive with a few minutes to go, so made the drive up to just short of milepost 9 in short order with less than an hour to sunset. After indicating the spot to the group, we spread out and set up gear, some focusing and aligning on the sun, me - I did a quick focus on the sun then set up and aligned on the profile of KPNO. I was concerned about some thin clouds moving down from the north, but there wasn't much we could do, so we waited.

Time zipped by quickly and seemingly before I knew it, the disk of the sun became visible in the upper corner of the frame. By the time I determined the correct exposure, it had just touched the mountaintop observatory and I started the timer sequence with an exposure every 4 seconds. Bill, our former club president was worried it wouldn't span the mountaintop and announced he was going to move a few yards - but we assured him all was ok and besides, sunset would be over before he would be able to reacquire the image! And then it really was over. The alignment was perfect, everyone got some great images and all were carrying a silly ear to ear grin. And what was interesting, there was actually a group of sunspots visible - the first in a long time. In the shot here it is just above the University of Arizona's 90 inch telescope - second from the right.


I had read a notice online that the moon and planet Mercury would appear in the sky together, so some of tarried a bit while others packed up the the rapidly dropping temperatures. While we waited Melinda and Jennifer compared silly-looking hats.The moon was almost exactly 36 hours old - a skinny crescent that suddenly seemed to appear out of the darkening sky and a surprisingly bright Mercury less than 5 degrees away. A striking sight with the still orange clouds that glowed after the sunset.


We finally ambled to town and a small subgroup of us stopped for some pizza and beer before finally heading home to download images from our cameras. While my focus and the sunset alignment was great, I inadvertently had overexposed my shots very slightly and the red channel was saturated (since the setting sun is mostly red). It does affect the image some, but it is what it is - will just have to do it again and be a little more careful next time. I did make a quick movie of the exposures I took - we couldn't figure out how to display it here on the blog, but our friend and co-observer Tom Polakis agreed to host the .GIF file on his photo site. If your computer connection can tolerate downloading a 5MB file, take a look at the sunset movie. With the clouds moving in front of the sunset, it is quite incredible.


In the next few days the sun moves a little too far south to align with KPNO, but in a week it will be heading north and the alignment will happen again. The next chance is on Friday 25 December (yes, sunset on Christmas Day). It will be a good pass - if the weather is good I know at least one of our group will be doing it again with me...

(Click on the picture to open and view the .gif file. This is a 5MB .gif file, so it is very large!)

More Sunset Fun!

We certainly hope that all of our regular readers (all 5 or 6 of you!) have gone to Youtube and checked out the spectacular sunset alignment video we posted way back 10 days ago. Partly because of that success, we got to repeat the sunset trip several times, setting a record of 4 attempts this season!

Adam Block, who runs the SkyNights program on Mount Lemmon had a large group going up for the lunar eclipse on the 20th. Unfortunately, while we had some views of the sun while we set up the 5 telescopes (!), the sunset was totally socked in, and other than the view of Kitt Peak telescopes, the group of 25 people were skunked on the sunset observing. At least we tried! I think they had at least partial success on the lunar eclipse observing like we did in town...






Our next try was on Christmas eve the 24th. Friends Tom and Jenn came down from Phoenix to join in the fun with at least 3 other TAAA members. I was thinking that the only way we could improve on our sunset video from the 18th was to do it in the light of Hydrogen Alpha, using a special filtered view that normally shows dramatic activity in the light of a primary hydrogen reaction. When you see images of the sun showing large flame-like structures off it's edge (called prominences), it is likely an Halpha image. Tom is about the only person I know with such a setup, so we supplied Melinda's camera for another video, and he supplied the scope and mount for the partnership. He also shot some white-light shots with a telephoto and through his 10" telescope.

The attempt was partly successful for us. There was indeed a nice prominence that was visible that was just about the last part of the sun to set, but because we needed to use a diagonal in the filter train, the video is flipped left-to-right. Rather than show an inverted video, we show some individual frames here that we flipped in Photoshop. To show the prominence, the disk needs to be overexposed some, and it is hard to coax good views of the prominence so low to the horizon, but I think we did ok (barely visible at the top of the frame). Everyone in the group was successful, even though we were once again shooting through some thin clouds in the west. First timers Jim and Susan O'Connor even had one of their images picked as the solar astronomy picture of the say!

Tom and Jenn stayed the night at our house (we dined on crock pot chili that was waiting for our return from the sunset), setting up Tom's 10" to look for the storm on Saturn in the early morning hours. Unfortunately, the atmospheric seeing was so bad, we could barely tell that the planet had rings!

About the time they took off for Phoenix at noon the next day, another friend Laurie arrived (another Phoenix refugee). She was also interested in the sunset alignment, so we headed up once again. Unfortunately, we were shooting through thin clouds again, and while the video was fine, the blustery wind we had was really shaking the mount, almost inducing motion sickness watching the movie! With the clouds we had more spectacular colors, and we paused at another pullout on the way down to watch the city lights come up against the dimming twilight. Laurie had a great time documenting it all.

So for this December 2010 solstice sunset season, we were 3 successes for 4 attempts. The alignment seems perfect - that pullout at milepost 8.7 seems the perfect place to be when the sun reaches -23.40 degrees declination. It was interesting that none of the 3 "clear" sunsets were actually perfectly clear, but we had great views of each anyway. And even though we got that perfect video on the 18th, well likely do it again a few times next year!

Five Sunsets!

We've just passed the Winter Solstice, and for those that know me, it's the season for imaging the setting sun past the silhouette of Kitt Peak National Observatory. Like the ancients gathered around Stonehenge for celestial alignments, I've been drawn to this one for well over 20 years, first recording the sunset behind the Observatory in 1988! Those days was with my 12" Newtonian telescope and film (!) camera pointed out of my old van! It is much easier now with portable refractors and digital cameras. I can park and be set up in minutes these days. At left is a GIF file I put together on the "optimum" date of 17 December - click for a larger version. At right is shown my current setup - TEC 140 triplet apochromatic telescope and the venerable Canon XSi camera. Note the home-built solar filter that we made in the TAAA filter workshop about a month ago - it has gotten lots of use lately!

The GIF image at left is quite remarkable. While it shows a few circular artifacts that I didn't see in the original files, what is amazing are the layers in the atmosphere. Formed from air at different temperature profiles, you can see their effect on the image both at the suns edge, and also in the appearance and spacing of the two sunspots. It looks like watching an image at the bottom of a wavy pool!

Why the "Five Sunset" title? Well it hit me that I really didn't know how the image correlated to Kitt Peak very exactly. I knew if you were at "the spot" a few days before and after solstice, you could catch the alignment. I wanted to learn a little more about the situation. About the time I decided to do this, it was 10 days before solstice, so went up alternate days 5 times. It really was an amazing experience! Every sunset was different. Most were clear, one had some clouds during sunset, the last night it completely clouded up 30 minutes after sunset.

The end result is shown here at left.  I started on the 13th, when the sun was still moving southward more than a fifth of its diameter every 2 days. Of course, its southward motion slowed and stopped on solstice day on the 21st, taken just a few hours before the start of Winter. While the casual observer might think the sun wouldn't cover the observatory on most of those dates from this image, note the suns sweeping left-to-right motion for us here in the Northern Hemisphere. Because of the horizontal motion, I caught the full Observatory silhouette on 3 of the 5 evenings, all observations from the exact same spot. As you can see at right, after the first alignment happens about the 17th, the sun continues to move southward, appearing to lower from day to day as it sweeps past the Observatory. On solstice day, it BARELY covers the full silhouette - it helps to move northward as far as you can along the curve to help you catch more solar disk.

But the silhouette wasn't the only thing to see! Like I said above, every one was different - the first day it was very hazy - at least the inversion layer was above the observed level of Kitt Peak and it appeared very hazy. The result was that when the sun dropped below the observatory profile, the peaks projected their shadows into the hazy air, shown at left. Similarly, the next trip up on the 15th, I was shooting the disk (Meade 80mm F/6) as it dropped below the mountain and I caught a bit of blue/green flash between a crack in the mountain, and at the same time, caught more rays being cast upwards and outwards from the suns position, shown at right.



It often paid to not to hurry home. On the evenings when there were clouds, there were spectacular sunsets. At left is a nice example - a 3-frame panorama taken with a 300mm lens plus a 1.4X tele-converter. On another night, I had planned to pause at "Bad Dog" (actually Babad Do'ag) overlook near the lower slopes of the Catalinas to shoot Kitt Peak silhouetted not by the setting sun, but with late twilight glow with the city lights in the foreground. At right is a 5 frame panorama taken with the Meade 80mm F/6 (480mm focal length) and 10 second exposures. I love catching the contrast of the dark-sky observatory within view of the urban lights of Tucson. Besides the lights of Tucson's downtown skyline, the bright lights are from the UA football practice field, where the team was practicing for their upcoming bowl game.

I've got some more items of interest here, but will have to wait for a subsequent post.

An Alignment Scout Trip!

I'll bet you thought with the solstice sunset alignment with Kitt Peak 10 days ago that that stuff would be over for the season, but you would be wrong!  Again, based on my daily astronomical on-line reading, I "discovered" that in a week or so Mercury and Venus would have a lovely close conjunction in a week or so.  Knowing that Venus is in about the right spot to catch it behind Kitt Peak (again!) from the Mount Lemmon Highway, it was time to hit the road for another sunset!  Also, it is about the last field trip I'll be taking with the ole' Ford '88 van with the smashed-in rear end.  I take it and sign it over to the insurance company Wednesday...

Anyway, I made it out to "Bad Dog" over look (Babad Do'ag  for sticklers...) at about milepost 3 on the Mount Lemmon Highway just in time to catch the sunset.  Shown at left, it went down about 2 degrees south of where it needs to intersect the Observatory.  According to my calculations, for those who might want to observe the alignment of the sunset w/Kitt Peak at this lower location, rather than the one near MP9, Friday the 16th is the day to be at the "Bad Dog" overlook.  It moves much more every day than near start of Winter, so you only get the one chance on this side of solstice.

But I didn't come today for the sunset, only to get there before it got dark to get setup!  BTW, with snow atop Mount Lemmon, the highway was packed with cars heading down.  Luckily I had this lower overlook mostly to myself most of my 80 minutes there.  Venus popped out shortly after sunset, and about 10 minutes later, Mercury was spotted below the brighter planet.  Still a few degrees apart, by this next weekend they are less than a degree apart.  Waiting for it get dark enough to have it stand out from the sky and get a little lower with Tucson's city lights as well, it is shown at left.  That is Venus above and Mercury mostly below it and a little to the right.  I waited another 10 minutes to catch it just before Mercury set behind the Quinlan Mountains.  While the sky is darker, the rising Full Moon behind me helps light up the "A" of "A" Mountain, and in fact, the telescopes atop Kitt Peak have the pale illumination due to the moon.  In the next few days, Mercury will rise up nearly to the height of Venus and both will move to the right a couple degrees, so should be a pretty pair directly above the Observatory.  Perhaps I'll see you there!

I also had time to take a 5-frame mosaic of the pretty lights of Tucson with Kitt Peak in the background.  Down-sampled here to the 1600 pixel-wide maximum, you can't see a lot of the details of the original mosaic, but you can perhaps see why I do them to keep the details of the original files...  I also took a time-lapse of the twilight including the swiftly moving clouds...  Perhaps I'll be doing something with that soon.  I guess I'm just easily entertained!

Earliest Sunset!

Here we are on the 5th of December, a good 2 weeks till the Winter Solstice, and yet, if you look at a table of sunset times, right now is the time of earliest sunset!  "Wait", I can hear you all say - "I thought that happened on the first day of Winter on 21 December!"  Well, you would be partly right - the shortest DAY occurs on the first day of Winter in the northern hemisphere, when the sun follows its lowest arc across the sky.  Referring back to that table of sunset/sunrise times, you will also note that the date of latest sunrise occurs in mid-January, a couple weeks AFTER Winter Solstice.  So the shortest day happens on 21 December, but because the Earth's orbit is not completely circular, but slightly elliptical, the earliest sunset, latest sunrise and shortest day do not all fall on the first day of Winter.  If it did, life would be a little more boring, and we wouldn't be able to use these tidbits as excuses to learn something new.  But do go check out those sunrise/sunset times - you will see I'm right!  You can think of it this way - with the sunset time getting later day by day, it won't be long till the Winter that isn't here yet will give way to Spring and Summer!

 

Oh, and the picture above - taken a couple months ago from Kitt Peak National Observatory with my little Meade Telescope - an 80mm diameter apochromatic refractor, F/6, with a 480mm focal length and Canon XSi camera.

Now It Feels Like Christmas!

In what has become an annual holiday tradition for a bunch of our friends, this evening we made the trip up the Mount Lemmon Highway to again observe the winter solstice sunset alignment.  The trip up was clouded out last weekend (plus, we had a holiday party to attend), so tonight was the last chance this season.  It was a last minute decision to attend for me, plus Melinda had to work, so there was a rush to prepare a scope and camera.  Five cars met at Tanque Verde and Mount Lemmon Highway at 4pm for the 20 minute drive up near milepost 9.  I decided to again use the Celestron 5" telescope, which just about gives the perfect image scale.   After careful focusing on the sun, it was about a half hour wait to sunset.  Note that we had a good supply of sunspots this year.  The image at left was taken at setup with the sun about 8 degrees above the horizon.  Up is up in this image, so north would be to the 2 o'clock position.

Shown here are Susan and the Jims waiting for the sun to approach the horizon.  Jim O'Connor had both a small scope with a white-light filter, and one with a Lunt H-alpha filter shooting video.  Realize we're all parked next to a relatively busy highway, with lots of tourists driving cars and trucks covered with snow they are bringing down from the mountaintop.  A few shouts, but on Christmas eve, no one stopped to see what we were doing this year.

Finally the sun dropped into our viewfinders and shutters started snapping.  I pushed the start button on my timer, and after a quick check for the proper exposure, mostly I stood back and took a snap or two with an unfiltered telephoto lens on another camera.  Before you knew it (always seems to happen faster than you think), the disk dropped below the Observatory and it was over.  As soon as I stopped taking frames every 3 seconds and removed the filter for a few post-sunset shots, I could see the scope was a little out of focus, as well as suffering from shutter-shake.  Unfortunately, after setting focus during setup, the temperature dropped enough to shrink the telescope tube and throw it out a little...  But the experience of a mountain sunset in a perfectly clear sky among friends made the trip worthwhile, even with fuzzy pictures!

After packing up and heading down the hill, my friend Mike and I stopped at the Babad Do'ag overlook (Tohono O'Odham name - Frog Mountain, for the Catalinas) for what has almost become as popular to me as the sunset - watching the twilight fade as the lights of Tucson come up.  I set up my camera and tripod again and exposed a few panorama mosaics, then focused on the silhouette of Kitt Peak and it's telescopes against the last of the twilight with foreground city lights.  It is fun to locate the hot spots around the valley by their lights at night.  Our downtown district doesn't have the skyline that many large cities have, but it was easily identified by it's proximal alignment from our observing spot with Kitt Peak.  Hopping to the north from downtown the University and UMC could be located.  Even darkened locations like A Mountain and Gates Pass could be spotted in the exposures that were up to 20 seconds.  Finally it was time to head back to civilization - I had cats to feed, presents to wrap, and a cheesecake to bake as gifts to friends.  It finally felt like a holiday!

Holiday Sunset Alignment!

It is that time of year again - if we are nearing the winter solstice and the holidays are upon us, it is time once again to travel up the Mount Lemmon Highway to once again document the sunset alignment against Kitt Peak National Observatory. I feel like an astronomer of old, looking for alignments to tell the turning of the seasons, and indeed this is true. From "my spot" (about milepost 8.7) along the Mt Lemmon Highway, the alignment is nearly perfect when the sun hits a declination of -23 degrees, 24 minutes which happens on the sunsets of the 18th and 24th this year. All of the telescope domes atop the mountain will fall within the observed disk of the sun.

This year we had 3 other TAAA members observing with us. Meeting at the base of the mountain at McDonalds at 3:30, it was a 30 minute drive up to the spot, providing plenty of time to set up equipment. This year, rather than take still images every few seconds and turn them into a movie like last year, we decided to use Melinda's T1i to take HD video - duh! It should look much nicer, and at 30 frames a second, with sound besides, it should be the ultimate reproduction of the sunset. Besides Melinda's Canon T1i, I also used the Celestron 5 I got from Elinor and David Levine - it provides the perfect image scale for the moon or sun to just fill the short axis of the APS-C sensor. I practiced using the video mode the night before on the moon, and freshly collimated on a star to provide the sharpest images.

While the alignment has been reduced to a science (no question anymore of a perfect alignment), the weather conditions were questionable even as we met at the base of the hill. High clouds were gathering and they looked even thicker towards the west, but we were all motivated to try, so off we went. After setup, focus and alignment, we got to gather, offer advice and guidance as "magic time" came. It appeared luck was with us as a clear strip appeared over the mountain, from our vantage point at least, 60 miles away. As the sun moved ever closer to the horizon, it finally came into the telescope's field of view and I pushed the "record" button. I was anxious as a cat near a rocking chair, but the image on the camera screen looked just about perfect. After the sun disappeared behind the 90" telescope, I removed the solar filter and recorded the sunset colors for a couple more minutes. In all, we got nearly 9 minutes of video, recorded at the medium-HD resolution. Still, it is about 1.4GB, so impossible to display on the blog at anything approaching full resolution - we'll have to see how we can display it publicly. Shown here are a few frames pulled from the video... It was fun gathering around and watching the replay. Playback at normal speed with the sound is quite fun, approaching the anticipation of even a total solar eclipse as it progresses!  {We have uploaded the video to YouTube.com.  If you click on this link "Mt. Lemmon/Kitt Peak Sunset" you will be able to watch it!  Remember, it is a huge file and if you have a slow internet connection it may take a very long time.}


But the fireworks were not quite over. Even well after the sun had gone down, the western sky was ablaze with color and shifting clouds. This was, without a doubt, the most amazing, dynamic sunset I've seen. Cloud patterns and colors shifted minute to minute and it seemed to go on for much longer than most colorful sunsets. Just amazing! And for dessert, we stopped on the trip down the hill at one of the overlooks showing the city lights, Kitt Peak far in the distance (the flat-topped mountain on the horizon). We continued on to a holiday party at my boss', but what we had just witnessed will stay with us for a long time!

A Great Alignment and Spectacular Sunset!

Last evening was our first opportunity this year

to observe the sunset alignment of Kitt Peak National Observatory.  About 4 or 5 days before and after the Winter Solstice, it can be observed from a broad pullout on the outside of a curve just below milepost 9.  There is an unimpeded view of the Observatory to the SSW, and though sometimes the cars passing on the road are pesky, it is a safe place to observe the alignment.  It seems a tradition leading up to the holiday season to observe or shoot it and it would seem strange not to chase it - any excuse to get out and observe!  While it can be quite cold here in December above 5,000 feet elevation, yesterday we set a high temperature record of 83F in Tucson, so it was comfortable in long sleeves even without a jacket...

I always have fun trying new imaging options every year, and there was no exception this year.  Our friend Roger, a telescope maker of some renown, built a 5.75" F/8 diameter triplet apochromat a few years back, and I talked him into joining us, and running Melinda's T1i on it.  The 1170mm focal length was perfect for the sun's diameter on the APS sensor.  I quickly adapted his mounting plate to a massive tripod I've had for decades, and the combination was quite robust.  The pictures were taken shortly after we arrived with the sun still a good 10 degrees off the horizon.  Yes, we had some thin clouds, but perfectly clear skies usually make for boring sunsets!

We had a few friends joining us this year from the Tucson Amateur Astronomy Association (TAAA).  Alan Strauss,director of the Mount Lemmon Sky Center, joined us with some small scopes, one for white light and another for H-alpha viewing.  In the image at left, Alan is standing at right talking to Roger, behind his blue telescope, with Melinda sitting in the back of the van.  Jim Miller and his wife Elaine also joined us, setting up his 10" telescope - the picture at right shows him focusing for the sunset.

Jim O'Connor and wife Susan also came along, Jim attempting to take video of the event with laptop and Imaging Source camera (shown at left image).  We all arrived in plenty of time to get our equipment setup, and had a chance to socialize a bit before the sun hit the horizon.  We even had a couple of normally speeding cars stop and ask what was going on...  The picture at right shows the wide-angle view with the spare camera once the button was pushed and pics came crashing in...

Our observing setup is shown in a little more detail at left.  Roger's APO is the blue scope at left.  It has an older Thousand Oakes glass solar filter - a type 2 filter designed for imaging with short exposures.  Not entirely safe for visual observing (a little too bright), but perfect for shooting a dimmed sun on the horizon!  You can also see the kludged saddle plate mount atop my binocular mount to hold the telescope...  We also observed the sunset visually with a C5 telescope with Mylar filter and roof prism diagonal to give a correctly oriented view.  Through trial and error, I found I could shoot a full-size jpeg every 2 seconds with Melinda's T1i without problems, so that is how I shot it.  While the images were quite sharp when we set up, the seeing got quite mediocre a little before sunset.  I'm thinking it was the inversion layer that was very near the level of Kitt Peak, Roger thought it was cooling air falling down the slopes of the mountain we were on.  Effects of the seeing can be readily seen in the time-lapse below...

As soon as the sun entered the field of view, I
checked the exposure to make sure it wouldn't be overexposed, then started the exposure-every-2-second sequence.  Running manually, each was about a 2000th of a second.  As soon as the sun set below the mountain, I switched it to aperture priority automatic, and even through the solar filter, an adequate exposure was about a 16th of a second.  The image at left shows the sun perfectly centered on the Observatory outline.  Yes, the clouds made the pictures a little more interesting, and fortunately, there was a clear zone at the level of the telescope domes above Kitt Peak.  The sun always seems to move a surprising amount from left to right as it sets (because we're in the northern hemisphere).  It also seems to happen so quickly through a telescope, but takes about 2 minutes, telescope or not!  The last piece of sun set between the 4-meter telescope at right and the Steward Observatory scopes to the sun's left, the last bit bifurcated by the flat-topped dome of the 90".

Of course, we get some spectacular sunsets in
Arizona - something about the clarity of the air and the normally clear skies of the drier, more desolate desert to the west.  And did we have a spectacular sunset.  While normally the show is over once the sun sets, it just got more and more spectacular for the next 10 minutes!  While some of the first color shows up in the wide shot above while the sun was still above the horizon, a few minutes later with the sun illuminating the underside of the clouds, they just glowed...  I took a couple different styles of images - at left is an HDR (High Dynamic Range) which combines 3 exposures of different lengths to preserve details in both shadows and highlights of the image.  I wanted to preserve the purple illumination of the front side of the mountains, as well as the bright colors in the clouds.  At right is a 4-frame mosaic with my zoom's maximum 200mm focal length to preserve details of our view to the west from Thimble Peak at right to the south past Kitt Peak.  Of course, I'm limited to the 1600 pixel wide frame here, but it is a good representation of the spectacular sky.  I'm sure you might think that I've photoshopped in the colors, but check out Alan Strauss' post of the sunset and you will see that I'm not pulling your leg!

So finally, the 173 images collected, of both the sun setting and a minute of twilight skies afterwards, were assembled into a movie using Windows Moviemaker, then uploaded to Youtube.  It makes a very nice 30 second sunset time lapse, showing not only the motion of the sun, but also the slight motion of the clouds past the mountaintop.  You should be able to play the movie right here in the blog post, or you can hit the youtube icon at the bottom of the viewer to go to that site for viewing.  Enjoy!